1. Field of the Invention:
The present invention relates to an image processing apparatus having a function of projecting an image of an original on a screen, like an overhead projector, and a function of forming an image of the original on a paper or a transparent sheet, like a copying machine.
2. Description of the Related Art:
Conventional overhead projectors (hereinafter called "OHP") can be divided into two groups: transparence-type; and reflection-type.
In the transparence-type OHP, an original placed on a transparent support table is illuminated from the underside of the support table, and an image of the original is projected on a screen via a projector lens and a reflector mirror, both disposed above the support table.
In the reflection-type OHP, an original on a fresnel lens is illuminated from the upperside of the fresnel lens and a reflected image of the original is projected on the screen via a projector lens and a reflector mirror, both disposed above the fresnel lens.
Apart from a simple original that can be formed by manually drawing or writing a figure or a character directly on a transparent sheet with a pen, an ordinary original to be used in the OHP is formed by copying an image on a transparent sheet by using an electrophotographic copying machine, for example.
When giving a lecture, a presentation or a briefing by using an OHP at a school, a presentation site or a meeting room, it is necessary to prepare an OHP original in advance. Therefore, if there is no original, an unschedued material readily be projected on the screen, though an original may be prepared by copying
To this end, a solution has been proposed in which an OHP is combined with a copying machine, as illustrated in FIGS. 16 and 17 of the accompanying drawings, so that an original to be projected can be readily prepared by the copying machine. The prior art apparatus of FIG. 16 is a reflection type which comprises an original cover 203 openably mounted on an apparatus body 201, a reflection-type focusing plate 205, such as a fresnel lens, disposed on an upper surface of the original cover 203, and a projecting unit 207 disposed above the focusing plate 205. The prior art apparatus of FIG. 17 is a transparence type which comprises a support table 202 movably mounted on an apparatus body 201; when projecting, the support table 202 is moved away from a focusing plate 205 disposed on the top of the body 201, and the original on the focusing plate 205 is illuminated to a projecting unit 207 by a lamp 209 disposed below the focusing plate 205.
A problem with the reflection-type apparatus is that since the focusing plate 205 is disposed on the upper surface of the original cover 203, proper projection can not be made if the positional relationship of the lamp, the focusing plate, the projecting lens and the reflector mirror is not proper. The above relationship is regarded as one of the most significant factors in the reflection-type optical system. In this optical system, if the support cover 203 is shifted out of parallel relationship to the focusing plate 205, the center line of reflected and focused rays of light changes due to the shifted focusing plate is, thus causing a distorted image on the screen. Since this conventional apparatus requires additional means and space in order to eliminate the prior problem, it is impossible to make the apparatus light in weight and compact in size.
A problem with the transparence-type apparatus is that since the lamp is disposed within the body, the interior of the body would be heated by the lamp to a high temperature, which is very influential on various peripheral parts. Further, it is impossible to accomodate a roll of heat-sensitive paper in the interior of the body.
Another problem with the conventional apparatus is that since the support table is moved with the projecting unit and is supported over the focusing plate, the projecting unit would be a substantial obstacle while the original is being set on the support table or is being replaced with a new one. Yet if the projecting unit is merely folded over the body, then the support table cannot be moved without difficulties.
Further, since an OHF original is formed on an OHP sheet on a size equal to the size of the initial original, a setting surface of the reflection-type focusing plate requires a size substantially equal to that of the OHP original. Consequently it is impossible to reduce the apparatus to an adequately compact size.
Yet if the distance between the projecting unit 207 and the focusing plate 205 is reduced in order to provide a compact apparatus, the distance between the focusing lens 205 and the projecting lens 210 also necessarily varies, as shown in FIG. 22, thus requiring a wide-angle projecting lens. With such wide-angle projecting lens, a projected image would be irregular in darkness with marginal portions darker than the central portion.
A further problem with the conventional apparatus is that since in order to perform the copying operation when the lamp is on, the power source must be the sum of the consumed electric power of the lamp and the consumed electric power for copying, it is expensive to operate the apparatus.
If two separate power sources are used for the lamp and the copying, respectively, it is impossible to reduce the entire apparatus in weight, size and cost.
When the lamp is on, the lens surface of the focusing plate is high in temperature. Therefore it is very risky to perform copying operation while the lamp is on. This also gives an adverse influence on the temperature control of the thermal head.
With the conventional apparatus in which the support table is moved by a motor, since the power source is off and the support table is not locked while the apparatus is being carried, the support table tends to move due to the swinging motion of the apparatus being carried. As a result, the support table tends to contact the peripheral parts.